package servlet;
import pojo.User;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

@WebServlet(urlPatterns = {"/user"})
public class UserServlet extends HttpServlet {
    //art+insert
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        List<User> users=new ArrayList<>();//存储从数据库查询的数据
        //jdbc操作数据库--查询
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");

            // 2、获取连接(url,name,password)
            String url = "jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=utf-8";
            Connection connection = DriverManager.getConnection(url, "root", "123456");
//            if (connection !=null)
//                System.out.println("连接成功");
            // 3、写sql
            String sql = "select * from sys_user";
            //4、预编译sql
            PreparedStatement preparedStatement = connection.prepareStatement(sql);
            //5、有参数设置参数

            //6、执行sql
            ResultSet resultSet = preparedStatement.executeQuery();
            //7、遍历结果集
            while (resultSet.next()) {
                User user=new User();
                user.setId(resultSet.getString(1));
                user.setName(resultSet.getString(2));
                user.setPass(resultSet.getString(3));
                //把对象添加到集合中
                users.add(user);
            }
            //8、关闭资源
            resultSet.close();
            preparedStatement.close();
            connection.close();
            //9、 把集合中的数据存储到作用域中
            req.setAttribute("users", users);
            //10、跳转到页面
            req.getRequestDispatcher("/user.jsp").forward(req, resp);
        } catch (ClassNotFoundException e) {
            throw new RuntimeException();
        } catch (SQLException ex) {
            throw new RuntimeException(ex);
        }
    }
}
